SVI and VLAN Addressing Issues

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Each VLAN in the network required a unique IP subnet because two devices in the same VLAN with different subnet addresses, cannot communicate. During the VLAN configuration this a common problem, and we can solve this problem by identifying the incorrect IP address configuration and changing the address to the correct one.

For example, if you want to connect a client anywhere in the VLAN 10 then you must require a valid subnet configuration. If you want to communicate outside the VLAN you must require a valid default gateway. The default gateway must be the VLAN 10 SVI address.  In the figure below, the PC-2 cannot connect to PC-3 and PC-4, but PC-3 and PC-4 can communicate with each other.

SVI

A check of the IP configuration settings of PC-2 shown in figure-2, Reveals the most common error in configuring VLANs a wrongly configured IP address. PC-2 is configured with an IP address of 192.178.20.1, but it should have been configured with 192.168.20.1.

SVI Configuration

Solution

Change the PC-2 IP address to correct IP address 192.168.20.1. The PC-2 Ethernet configuration now shows the updated IP address of 192.168.10.1.  The Figure below illustrates the output on the bottom reveals that PC-2 has regained connectivity to the Web server found at IP address 192.168.20.1.

SVI and VLAN Addressing Issues 4

SVI Configuration

SVI is standing for Switched Virtual Interface. It is a routed interface in IOS representing the IP addressing space for VLAN connected to this interface. The VLAN has no physical interface so; the SVI provides Layer 3 processing for packets from all switch ports associated with the VLAN.

With this interface, the switch uses virtual layer 3 interfaces to route traffic to another layer 3 interfaces which eliminate the need of the physical router. For virtual interface configuration, ensure your switch has a VLAN represented by the SVI you want to create. The command are the following:

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